The White Sox made a move intended to shore up their defense Thursday, optioning second baseman Micah Johnson to Triple-A Charlotte and calling up infielder Carlos Sanchez to take his place.

Sanchez will join the Sox in Oakland for the start of a three-game series against the Athletics on Friday and is expected to take over the role as the primary starting second baseman, general manager Rick Hahn said via conference call. Hahn expects infielders Emilio Bonifacio and Gordon Beckham to remain in their current utility roles, which include occasional play at second base.

Defense has been a major issue for the Sox, who entered Thursday ranked seventh in the majors with 25 errors, and Sox manager Robin Ventura and Hahn repeatedly have said it needs to be a point of emphasis for the 14-17 club.

The Sox are hoping Sanchez, 22, will represent an upgrade in the field over Johnson.

"Carlos is going to bring a little bit more defensive consistency, solid baserunning," Hahn said. "He'll be a tough out for us. He's going to help stabilize that position."

Sanchez, who played in 28 games last year for the Sox, was in competition with Johnson for the job in spring training and spent the first week with the team this year while pitcher Chris Sale was on the disabled list. After he was sent down, Sanchez had a big first month in Charlotte, hitting .344 with 10 doubles, two home runs, 17 RBIs and five stolen bases in 29 games.

"He's still a relatively young player," Hahn said. "I think he's more coming into his own with the repetition at the minor-league level. … He got beat out for his job, but as opposed to hanging his head, he went down and worked his tail off and obviously had a great amount of success."

According to MLB.com, the 24-year-old Johnson entered the year ranked as the Sox's fifth-best prospect, while Sanchez, 23 on June 29, was ranked No. 10.

Hahn called the move a "minor setback" for Johnson, who hit .270 with two doubles, three RBIs, eight runs scored, five walks and 17 strikeouts over 27 games this season. Known for his speed, he was 3-for-5 on stolen-base attempts but also made some baserunning blunders.

The major concern with Johnson from the start was his defense, and while the Sox said he was improving while putting in a lot of pregame work with Ventura and other coaches, he still was shaky at times. He committed three errors and is ranked 23rd among qualifying major-league second basemen with minus-8 defensive runs saved, according to FanGraphs.

Garcia and LaRoche became the first Sox players to hit back-to-back...

(Colleen Kane)

Johnson sat out Wednesday's victory over the Brewers as Ventura went with a more defensively sound lineup that started Bonifacio at second base, Beckham at third and Adam LaRoche at first.

"From a defensive standpoint, he wasn't quite as consistent play to play as we needed him to be at the big-league level and as we expect him to be in the future," Hahn said. "He also had a couple of questionable baserunning decisions, which I think is a part of being young, and much like the defensive side of things, will get ironed out with repetition."

Hahn said Johnson was disappointed but maybe not too surprised about being sent to Charlotte, where he will continue to work as a second baseman. He compared Johnson's demotion to those of former Sox players Joe Crede and Aaron Rowand early in their careers.

"Both Crede and Rowand went on to become, for lack of a better description, White Sox icons of the modern era," Hahn said. "There is no reason Micah can't follow suit. This is a minor setback on the path to what we believe will be a successful big-league career."